1. Field of the Invention
This invention relates to a flash control apparatus on which an electronic flash device is mountable.
2. Related Background Art
It has heretofore been possible to drive discrete electronic flash devices mounted on the hot shoe and the synchro terminal of a camera at the same time, but there has been no camera which can drive such electronic flash devices independently of each other.
Also, when continuous photographing is to be effected by the use of an electronic flash device, the charging time of the electronic flash device is long and continuous photographing as desired cannot be effected, and an extraneous power source is used to shorten the charging time.
In the prior art, the synchro terminals of an electronic flash device mounted on a hot shoe and an electronic flash device mounted on a synchro terminal are merely parallel-connected in a camera body, and this has led to a problem that the electronic flash device mounted on the hot shoe and the electronic flash device mounted on the synchro terminal cannot be controlled from the camera body so as to emit light singly or emit light independently with a time lag therebetween and can only be controlled so as to emit light at the same time.
Further, when an attempt is made to cause the electronic flash device mounted on the hot shoe and the electronic flash device mounted on the synchro terminal to emit light singly, it has been necessary to remove the electronic flash device which should not be caused to emit light or to open the power source switch of the electronic flash device so as not to emit light, and this has led to a problem that the operation is very cumbersome.
As already noted the charging time of an electronic flash device is long and continuous photographing using an electronic flash device could not be accomplished as desired. Also, an attempt to shorten the charging time of the electronic flash device has made it necessary to supply an extraneous power source. However, the extraneous power source is bulky and bad in form, and further the shortening of the charging time has been limited in its possibility.
Besides the method of shortening the charging time of the electronic flash device by using an extraneous power source, a method of shortening the charging time of the electronic flash device in practical use will be considered hereinafter. For example, if two electronic flash devices are caused to emit light alternately during each cycle of photographing, the average charging time can be reduced to half. However, if the two electronic flash devices are merely connected together as in increased light photographing, the two devices will emit light at the same time and the purpose cannot be achieved.
Also, when an attempt is made to photograph with an electronic flash device mounted only on the synchro terminal, the synchro contacts of the hot shoe and the synchro terminal are connected together in the camera body. Therefore the electronic flash device may contact with the synchro terminal of the hot shoe side, which is exposed outside the camera body, thereby erroneously emit light. Also, when an electronic flash device from which a high voltage is output to the synchro terminal is mounted on the synchro terminal, there has been the possibility of the photographer touching the synchro contact of the hot shoe side by mistake and receiving an electric shock.
As means for solving this problem, it has been necessary to cover the hot shoe with a cap and prevent the contact with the synchro terminal, or to provide a switch between the synchro contact of the hot shoe side and the synchro contact of the synchro terminal side, and further provide a mechanism by which the switch is closed to connect the synchro contacts of the hot shoe and the synchro terminal only when an electronic flash device is mounted on the hot shoe.